In a image display device employing sub-fields to display gradation levels, such as a plasma display panel (PDP), image quality has often degraded by a noise generated in displaying moving image, known as dynamic false contours.
It is well known in those skilled in the art that the dynamic false contours can be suppressed by increasing the number of the sub-fields. In some kinds of the devices, such as PDPs, however, increase in the number of the sub-fields makes difficult to hold sufficient time for emission, resulting in lack of luminance. To address the problem above, some attempts have been made. For example, Japanese Patent Unexamined Publication No. 2000-276100 suggests that the number of the sub-fields should be kept relatively small and combinations of the sub-fields corresponding to the gradation level of an image to be shown should be controlled in the area susceptible to the dynamic false contours to enhance both of the moving image quality and luminance.
Employing the method, the conventional device limits the number of the gradation levels fro image display in the area showing moving image, and shows image by using a combination of gradation values relatively unsusceptible to the dynamic false contours; on the other hand, to maintain consistent gradation levels, a dithering process produces substantial gradation levels.
However, the conventional display device, detection of moving pictures was not designed to precisely correspond to the gradation display method employing the sub-fields; it has been waited for improvement in accurate detection in areas in which the dynamic false contours are prominently observed, or likely to occur.
To address the problem above, the present invention provides a gradation display device with a simple circuit structure, which can accurately detect the areas in which the dynamic false contours likely to occur.